Madison Taylor is a successful forensic psychiatrist with a happy life, which includes her beloved husband Jeremy. However, everything changes when Jeremy is tragically murdered during a home invasion. As Madison reels with grief and shock, she is approached by Francis Tate, the man who killed her husband. Tate claims to suffer from dissociative identity disorder and tells Madison that she is the only one who can help him.
At first, Madison is hesitant to work with Tate, but eventually, she agrees to interview him in prison. As she spends more time with him, she begins to believe that his condition is genuine and that he may not have had complete control over his actions. However, as she delves deeper into Tate's psyche, she starts to question her own sanity and whether she can trust herself.
Meanwhile, Madison's colleagues and friends begin to worry about her mental state, seeing the toll that Tate's case is taking on her. Her professionalism and ethics come into question, and she becomes increasingly isolated.
As the trial approaches, Madison realizes that she has become too personally invested in Tate's case, and she must find a way to distance herself before it's too late. The Madness Inside Me explores the complex and sometimes dangerous relationships between psychiatrists and their patients, and the havoc that can be wreaked when lines are crossed.